This has been done many times by several organizations.

In fact, don't be surprised if the traditional PBX vendor is the one who sold the replacement VoIP system.

There's nothing magical about a VoIP system except for it uses a corporate network to transmit and receive phone calls.

Features are still the same.

Call quality is just as good as or better depending on the setup.

It requires specialized knowledge to manage the infrastructure effectively as what was required with the PBX.

Biggest hurdle to overcome is ensuring the network itself is ready to support VoIP.

If not, then an organization will run into a bunch of issues.

Naturally you blame the VoIP system because it's the newest thing around.

But this can be avoided with a little planning upfront.

VoIP is a mature technology that's ready for action.

If you're reading this and you haven't upgraded yet to VoIP, what's holding you back?

It is very good to properly prepare. It is less daunting than you think but taking the correct steps will help you prevent issues later. This is a short and sweets version but should take you through the most important steps.

It all starts with planning and will/should probably involve the following:
1) See what you have now and what you would want to have.
2) Check what hardware and/or software you now have and what may need to be replaced to be able to use VoIP (if possible, make sure you use proper VoIP hardware/software, it’ll save you hassle)
3) Check your internal network and your internet connection are sufficient (possible the bandwidth but perhaps even more important, the reliability)
3) Check which quality VoIP provider offers the services you want/need with the right quality, reliability and stability (and price, of course ;-) )
4) Check they providers you are looking at can supply the type of number you need/want.
If you want to retain existing numbers, make sure that the VoIP Providers you are adding to your shortlist can actually port the numbers in.
5) Test 1 or more VoIP providers for quality, reliability, support, etc
6) Decide which provider you want to go with and discuss/order what needs to be done.
7) Get the order started and follow the instructions the new provider gives you. This may include when to notify the old provider about porting, if that is the case.

8a) Set up your equipment with the credentials of the new provider so you can test (and maybe already use) the connections and numbers before your porting date. Once the porting process starts it will take a specific time for the number to actually complete the porting. At this time it may go down a little bit but this should usually not be more than a few seconds/minutes.
Once your new provider notifies you the porting has completed, test and start using.
8b) If you are only getting new numbers, set up your equipment with the credentials from the new provider, test and start using.

PS If at any stage you are unclear or if you run into any issue whilst setting up or testing, get in touch with your new provider’s support for instructions and/or help.

I hope this helps and if you are looking for a business solution, you can always get in touch with us :-)

A short answer to your question is Yes, you it’s possible.

But there more to consider before migrating from PBX to VoIP.

First off: Checkout this article to learn what steps you should take for porting your number. The good news is you will not have to change your current phone number which is an important aspect of your company’s identity and you’d like to keep it to be in touch with customers.

PORTING YOUR PHONE NUMBER IS NO LONGER A PROBLEM

If you’re doubtful and just ask to make sure of it’s worth to migrate your communication system to the cloud, will it be beneficial in terms of ROI?

THE FUTURE OF YOUR BUSINESS IS IN THE CLOUD

Feel free to write back if you have more question or doubts.

Cheers!

Victoria.

Basically, If you talk about an On-premise PBX system. which is not connected to a data network. you have to maintain its power supply and data storage by yourself. Also, it’s way more cost-effective in comparison with the VoIP calling system. It’s very reliable with scalability, monitoring on a single click up to 60+ business communication features at 99.99 uptime speed because it’s not dependent on a centralized power supply we are having multiple data centers just to give an HD calling experience all the time.

• Voice over Internet Protocol (VoIP) Basics

1. VoIP technology allows voice communication over the internet instead of traditional phone lines.
2. It converts voice signals into digital data packets and transmits them over IP networks.

• IP PBX Overview

1. IP PBX stands for Internet Protocol Private Branch Exchange.
2. It's a private telephone network within an organization that uses IP-based telephony.

• Components of an IP PBX System

1. IP Phones: These are endpoints in the system that resemble traditional telephones but use VoIP technology to make calls over the internet.
2. PBX Server: The central component that manages call routing, voicemail, conferencing, and other features. It's essentially the brain of the system.

• Call Routing and Management

1. When a call is initiated from an IP phone, it's converted into digital packets and sent to the PBX server.
2. The PBX server determines the destination of the call based on dialed digits, user input, or pre-defined routing rules.

To use VoIP(Voice over Internet Protocol), you need a modem and router. With the right software, you can call from any device, including smartphones and laptops. Many software provider companies in India offer VoIP services, so it's important to research and choose a company that meets your needs and budget. It's important to research software companies before investing. Checking reviews can help you make an informed decision. I'm glad that I had a positive experience with SAN Softwares. SAN Software offers affordable software with plenty of features. So If you also want any kind of software you can Connect with them.

Two key differences are cost and flexibility. Traditional PBX phone systems require a heavy investment in hardware. In addition to the costs of buying and setting up the telecom equipment, the providers have to cover the costs of all that copper wiring connecting clients with the exchange. The expenses do not cease with installation since these systems also require continual maintenance. System upgrades also necessitate buying and installing new equipment. All of these expenses need to be taking into account when setting realistic prices to charge the clients.

This reliance on fixed equipment limits the flexibility of traditional PBX system providers to quickly respond to changing customer requirements. For example, adding lines or activating new features necessitates sending out a phone engineer to the customer premises. There are also usually extra charges for upgraded phone equipment.

IP PBX systems do not have all of these big hardware expenses. They transmit calls over the existing internet infrastructure. Customers can use VoIP phone systems on their smart phones or computers - they do no need to pay for any special phone equipment. When they want to add new lines or activate other features, they do not need to call out an engineer. The customer can make these changes via the provider’s website. The lower costs of VoIP systems enable the providers to significantly reduce charges to their customers. The greater flexibility is another attractive factor as it gives the customer the ability to customize their business phone system.

The Pros & Cons of Cloud PBX vs. On-Premises PBX Systems

What is a Cloud PBX?

A cloud PBX, better known as hosted PBX, is a business phone system that runs over an internet connection. You don’t need to have Private Branch Exchange (PBX) equipment in your location — a VoIP provider does it for you

.

What is Onsite PBX?

Onsite or On-premise PBX is the traditional PBX phone system. In these phone systems, all the hardware is present at the physical location. Calls made through the on-premise PBX goes through your call server over a dedicated voice network connection.

While initially, it may seem that on-premise PBX is a good option, it has its fair share of disadvantages. Onsite PBX incurs high installation charges. It also requires full-time maintenance. In addition to this, the onsite PBX needs service and support from an in-house IT team.

Cloud PBX vs Onsite PBX

By now it is clear that opting for a cloud based PBX is a better choice as you will be able to reap more benefits when compared to onsite PBX. However, while making your decision to choose between the two, it is important to consider various factors. Here are some pointers to help you :

• Does your IT staff has the technical skills to manage an on-premise communication set up?
• What will be your budget and preferred pricing model?
• Do you have offices in multiple locations or remote workers?
• Will your existing systems integrate with the new communication system?

In accordance with the ongoing trends and market scenario, for most of the businesses, Cloud PBX is the way to go. Going forward, we will understand the benefits offered by these systems.

Essentially, a cloud PBX provides all the functionality needed in an office phone system such as voicemail, call forwarding, and of course, calling. Instead of setting up a server you have to maintain, you’d use a VoIP provider for your company’s communications.
When your staff answers or places calls, VoIP handsets convert the sound into data packets. These packets travel over the internet to the hosted PBX provider. The provider establishes a clear calling path between both parties. When needed, hands off to the Public Switched Telephone Network (PSTN).
Once data packets reach their destination, the business phone system converts them back into sound. It does all this within milliseconds without any extra configuration. See this diagram below to visualize the process. Here’s a diagram for what it would look like for a single office.

All you need is a reliable broadband connection to use a cloud-based PBX. The underlying technology accepts all kinds of IP phones, including desk phones, smartphones, and conference phones.
There are some practical business benefits you should know before getting a free quote.

Advantages of a Cloud PBX

1) Powerful features level-up your workflows

There are many more built-in VoIP features offered by a hosted PBX compared to an on-premises PBX phone system. These advanced features are the ones stakeholders care about most. Expect them to show up on a VoIP requirements list.
Several of the top cloud PBX features include:

• Mobile device support (mobile apps)
• Voicemail to email transcription
• Auto attendants (call flows)
• Automatic call recording
• Intelligent call forwarding
• Built-in video conferencing
• Inbound call queuing

Company leaders will appreciate that there are dozens of VoIP features available that don’t require any technical setup. Your phone system can also integrate with other essential tools like your organization’s CRM.
These added capabilities mean you can get more work done with enhanced productivity.

2) Flexibility for all locations and seasons

A flexible phone system means it can adapt to the changing conditions in the workplace. You can customize your phone system around your business needs versus feeling constrained by an old PBX.
There’s nothing more frustrating as an IT manager than unexpected business changes. You can say yes when the boss asks you if it can be done — without coming in on Saturday.
Small businesses enjoy total control over their company’s phone system. It’s easy to add and assign business phone numbers to your team. It’s even easier to equip your remote team with phone service.
In the era of remote work, employees can stay connected with a robust VoIP softphone app. Alternatively, you can have them take their office desk phone home.
When you increase demand, such as holiday sales, a hosted PBX will allow you to increase your call capacity. Plus, you can add hold music and comfort messages in minutes. This way, you can bump up your call quality and customer satisfaction.

3) Worry-free reliability and uptime

What’s the cost of downtime for your business? From tarnishing brand trust to losing revenue and sales, you can’t afford to deal with outages.
Luckily, a cloud PBX keeps you always reachable. A reputable service provider will offer 99.999% uptime, which is the gold standard for enterprises. Read what customers have said about them on social media, such as Twitter. You’ll get a sense of the reliability provided by the cloud PBX provider.
This increased reliability is made possible thanks to a redundant network of eight separate data centers. VoIP can work even during a power outage. You can route calls to different locations, including mobile phones, within seconds. On the flip side, a traditional phone system can crash due to weather, power failures, and other disasters.
Nextiva has invested millions into building one of the largest, most reliable business VoIP networks nationwide. Even if one of our data centers goes offline, there are seven more to handle the calls.
Related: Is VoIP Reliable? Nine Helpful Tips You Must Know

4) No maintenance

Lack of maintenance is a tremendous advantage of cloud PBX systems. System updates, network routing, adjusting VoIP codecs — it’s all handled by the hosted provider.
IT leaders and CIOs deal with a lot of fires throughout the week. (We hear you!) You can empower select people to make changes to your phone service online. Today’s VoIP phones are hassle-free, so it means fewer helpdesk tickets.
The problem with on-premise PBX systems is maintenance doesn’t stop when you hire full-time support. Having a technician available at all times is great, but you have to budget for $74K annually.
Businesses today have to get more done with less. It’s why switching to a cloud solution is a sensible investment. Get ready to say goodbye to a bulky on-prem communications system and costly VoIP maintenance contracts.

5) Unparalleled security

Cloud PBX phone solutions offer higher security compared to traditional PBX. When you have a physical landline, it’s up to you to ensure no one gains access to it. Many PBX systems are vulnerable to outside attacks, and audio signals they transmit are much easier to intercept.
Some hosted PBX solutions offer call encryption and 24/7 server monitoring. VoIP providers are consistently validated by third parties to check for compliance. VoIP security also means there’s the benefit of certifications like ISO/IEC 20071, PCI compliance, and HIPAA compliance.
Voice over IP itself is both reliable and secure, thanks to the redundancies of IPv4 routing. Encrypted voice packets and signaling works by using TLS and SRTP protocols.
Simply put: A cloud PBX lets you sleep at night. The backbone of your business communications is secure and resilient to bad actors.
Related: VoIP Hacking: How It Works & How to Protect Your VoIP Phone

6) Cost-effective for all companies

You’ll save a ton when you upgrade to VoIP service. Compared to a traditional PBX, premium features are either included or available for a low cost.
The team at Rackspace studied the total cost of ownership of cloud-based solutions. For every $1 spent on hardware upgrades, companies can expect to pay $2 for maintaining and securing that infrastructure.
This statistic should be alarming. On-prem voice equipment can cost you twice as much as you think. Make sure you think about the additional, indirect costs beyond the list price.

Here are the areas where a hosted PBX can lower costs:

• Workforce: Unless you’re a pro at SIP trunking, you’ll want dedicated IT staff or at least on-call IT support.
• Equipment: Use the equipment you already have, such as softphones. You can also rent VoIP phones for lower upfront costs.
• Maintenance costs: You won’t need to pay extra for software, security patches, or firmware updates.
• Adding phone lines: New employees and departments don’t have to wait to get calling.
• Calling costs: Enjoy the freedom of unlimited nationwide calling and low-cost international calls. Likewise, you can block international calling as well.

These cost savings add up. Sure, the switch might be a bit of work, but the payoff is immediate. It’s not hard to understand why over 100,000 businesses have already switched to Nextiva.

An IP phone system is a telephone system that uses the internet to make and manage calls instead of traditional phone lines. It stands for Internet Protocol Phone System, and it's a modern way to handle business communications.

Now, let’s break down what an IP PBX telephone system is:

✅ What is IP PBX?

IP PBX stands for Internet Protocol Private Branch Exchange. It is a business phone system that:

• Connects internal phones within a company
• Routes calls using the internet (VoIP - Voice over Internet Protocol)
• Replaces old traditional PBX systems that used landlines

🧩 Key Features:

• Call Routing: Directs calls to the right person or department
• Voicemail: Lets users receive and manage messages easily
• Auto Attendant: Answers calls and provides menu options
• Call Recording: Records calls for training or quality checks
• Conference Calling: Allows multiple people to join a single call

💡 Benefits of IP PBX:

• Cost Savings: Cheaper than traditional phone systems
• Scalable: Easy to add or remove users as your team grows
• Remote Access: Works well for remote or hybrid teams
• Advanced Features: Like voicemail to email, call forwarding, and more
• One Network: Uses your internet connection for voice and data

🏢 Who Uses It?

• Small to large businesses
• Call centers
• Companies with multiple offices or remote workers

In simple terms, an IP PBX system is a smarter, internet-based phone system that helps businesses handle calls more efficiently while saving money.

Differences between PBX and VoIP are:

1. Investment

A) PBX: Installing on-site PBX is a big project and requires a huge upfront investment.

B) VoIP: With VoIP, the main piece of hardware you need to invest in is IP phones.

2. Costs

A) PBX: Depends on set-up.

B) VoIP: Follow a subscription model.

3. Call Quality: The voice quality of PBX systems can be equally high. In fact, most modern PBX systems use VoIP technology.

4. Emergency Calling: Both VoIP and PBX numbers are different from regular phone numbers. They don’t have a clear, connected location.

5. Security:

A) VoIP security varies from one service provider to the next.

B) On-site PBX routes external calls directly to the PSTN. Since the system is not connected to the internet, there is no risk of hacking.

Hope I’ve answered your question. Happy Learning!

Hi there! Let’s see:

Think of VoIP (Voice over IP) as a way to make phone calls using the internet instead of traditional phone lines, and IP PBX (Private Branch Exchange) is like a sophisticated switchboard for managing calls within a business. Here’s how you can integrate them:

• Choose a VoIP provider: First, you need a VoIP service provider to handle the actual transmission of calls over the internet.
• Ensure compatibility: Your IP PBX should be VoIP-compatible (many modern IP PBX systems are). If not, you may need to add a VoIP gateway, which acts as a bridge between traditional telephony equipment and VoIP.
• Configure SIP trunking: VoIP often uses something called SIP (Session Initiation Protocol) trunks, which are digital phone lines that connect your IP PBX system to the VoIP provider. The provider will give you details like the SIP trunk address, which you’ll configure in your IP PBX system.
• Network setup: Ensure your network can handle the added traffic of VoIP calls. You’ll want a solid internet connection with Quality of Service (QoS) settings to prioritize voice traffic. This prevents call dropouts or bad call quality.
• Test and fine-tune: After integration, test the system thoroughly. You might need to adjust settings to get optimal voice quality, like jitter buffers (for handling network delays).
  
  Hope this helps! Have a great one!

The way I see it, it all simplifies to convergence. Why it is true that it can cannibalize their own T1 service, there is a major advantage to that. T1 can be ordered in two flavors: Voice (mostly PRIs) and Data T1 (1.544 Mbps). Since both are dedicated circuits, they can be managed by the provider, in this case at&t and provide a higher level of service.

A hybrid T1 service came about where, without getting deep in the technology side, basically allows for a single T1 to be used by voice ad data depending of what is and what is not being used. Since a T1 has 24 channels (23 on a PRI and the 24th for signaling) a voice T1 usually manages 24 digital lines for conversations when trunked to a PBX. Each one of those channels also provide 64Kbps so the hybrid version can provide say, 11 phone calls and 64K x 13 Channels for a total of 312K data connection. As soon as a voice port becomes available it adds more data. Please note this is a simple explanation for a non tech reader, a telephone specialist will feel this a bit short but for the purpose of illustrating and explaining I had done it this way.

Now, having said that, as long as at&t can provide a data connection of any sort (T1, metro ethernet, DS-3, fiber, etc) to the same customer and run the VoIP or Hosted VoIP Telephone service over that line. They can manage an end-to-end network and keep the customer with a converged voice and data solution that requires significant less resources than traditional voice T1 dedicated circuits while maintaining higher margins. It is important to mention also that by adopting these types of solutions they can significantly lower truck roll out for MACs (moves adds or changes) since all IP based network equipment can be managed and upgraded remotely.

Hope this helps.

Integrating VoIP telephony with an IP PBX system can streamline your communication infrastructure, enhancing both efficiency and flexibility. Here’s a step-by-step approach to achieve this:

1. Choose the Right IP PBX System: Select an IP PBX system that supports VoIP protocols. Ensure it has the necessary features and scalability for your business needs.
2. Configure VoIP Settings: Access the configuration settings of your IP PBX system. You’ll need to input details such as SIP (Session Initiation Protocol) server addresses, port numbers, and authentication credentials provided by your VoIP service provider.
3. Set Up VoIP Accounts: Create VoIP accounts within your IP PBX system. This typically involves adding SIP trunks or extensions, setting up call routes, and configuring voice quality settings.
4. Test the Integration: Perform thorough testing to ensure that calls are being routed correctly, audio quality is acceptable, and all features (like voicemail, call forwarding, etc.) are functioning as expected.
5. Monitor and Maintain: Regularly monitor the system for performance issues and update configurations as needed to adapt to changes in your business environment.

For a seamless and efficient integration, TeleCMI stands out as an excellent option. It provides a comprehensive solution that simplifies the integration process, offering advanced features and reliable performance to ensure your VoIP telephony and IP PBX system work together harmoniously.

To be honest, as someone in the industry, I think the metaphor that most customers have in mind is “root canal”!!

VOIP sucks. PBX sucks.

Having meaningful conversations with prospects & customers rocks. Helping customers rocks. Tech that gives your employees superpowers to do the right thing for said customers kicks butt.

VOIP and PBX technology implementations range from barely tolerable to just plain evil. For decades the best engineering in telecom went to core uptime features and usability always was last.

It took an injection of internet developers into the industry for people with a different mindset to start designing user-centric systems. Things are improving. But product that is more than 5 years old in our industry will probably most likely suck. Either a little or a lot.

I sometimes toy with the idea of a telecom product with a tagline “It doesn’t suck” - in our industry, that would be a good differentiator!

You can simply convert your landline phone to VoIP. You have to reach to CallHippo support team they will guide you how you switch to VoIP. CallHippo’s VoIP vendor provides an in-depth tutorial, so you don’t have to worry about it much.

VoIP or Voice over Internet Protocol is one such technology. There are many benefits of using VoIP phone services like flexibility, cost-effective, convenience, scalability, etc.

VoIP & PBX is like a Peanut Butter and Jelly sandwich. The two ingredients by themselves are okay. When you put them together, it’s delicious!

PBX and VoIP as a metaphor

Enough about food. The Private Branch eXchange (PBX) has been around for a long time

Voice Over IP (VoIP) opened up the possibility for voice to be freed from the confines of a traditional Telecom network

With VoIP being an application on an IP based network, like the Internet, there are countless examples of this technology in use daily. From taunting your opponent during an online game to FaceTime on an iPhone, VoIP is working hard to make life easier.

What’s even better is the transition of the PBX to the cloud. This movement has enabled organizations of all sizes to be able to capitalize on benefits that weren’t possible decades ago.

Remember that co-worker down town? They are now across the globe and connected to the same cloud based PBX.

In the case of your cloud based system, the ingredients (VoIP and PBX) aren’t as important as the innovations that come from taking a step towards the future.

A visual metaphor of the innovation coming from a PBX and VoIP foundation

Footnotes

To answer your second question: the tipping point began with Skype and continued when iPhone was launched. Let me explain. When Skype was launched, people realized there's a free alternative to costly long-distance calls.
With iPhone's launch, all of the sudden, millions of mobile subscribers had a device which is easy to download apps to (and for developers, great platform to distribute) and has the specs to support mobile VoIP demands. That, with 3G coverage have created the recipe for mass adoption of mobile alternatives to traditional calling.
So, it took quite a while for the carriers to move their gigantic ships into another direction, but, finally, they realized they must come up with an answer to those alternatives.
BTW, we've already started to see carriers providing their own version for mobile
VoIP. For example: T-Mobile's Bobsled and Telefonica's Tu-Me.

Hosted VoIP and on-premise PBX phone systems have their own benefits, but there are several advantages to choosing a hosted VoIP system over an on-premise PBX system.

Firstly, hosted VoIP systems typically require lower upfront costs than on-premise PBX systems. This is because there is no need to purchase and maintain expensive hardware. Additionally, hosted VoIP systems offer predictable monthly costs for phone service, which can help businesses budget more effectively.

Secondly, hosted VoIP systems are highly scalable, allowing businesses to easily add or remove phone lines as needed without the need for additional hardware or infrastructure. This provides flexibility and helps businesses adapt to changing needs.

Thirdly, hosted VoIP systems can be accessed from anywhere with an internet connection. This means that employees can work remotely or from multiple locations, making it easier for businesses to expand their operations without the need for additional infrastructure.

Fourthly, hosted VoIP systems are typically more reliable than on-premise PBX systems. They are backed by redundant servers and data centers that ensure continuous service even in the event of a power outage or other disaster.

Lastly, hosted VoIP systems offer advanced features such as voicemail-to-email, call recording, and call routing that are typically only available with expensive add-ons in on-premise PBX systems. These advanced features can improve productivity and efficiency for businesses.

They’re sort of synonymous these days. Both use Voice over IP protocols between the phone (or software phone) and the PBX. But, a cloud PBX is simply having the PBX live in a data center somewhere (AWS, Google, Oracle, etc.). Example companies that provide Cloud PBX would be Ring Central, 8x8, Dialpad or Call Centric.

On the other hand a local, non-cloud VoIP solution might have a VoIP PBX living on the organization’s premises. Personally, having been in the business for a while, Cloud is taking over. Mostly, because it’s cheaper and way easier to manage. The amount of hassle it takes to maintain your own on-premises VoIP PBX like Astra or Freeswitch doesn’t seem to be worth it when you can get a Cloud VoIP PBX for like $2–5 per user / per month (Enterprise level). Especially if you manage multiple locations.

Yes, TeleCMI is the best suited for VoIP minutes compatible with both softphones and virtual PBX systems. It integrates smoothly with popular softphone applications, allowing you to handle calls directly from your computer, mobile, or tablet without needing a physical phone.

For businesses using virtual PBX systems, TeleCMI offers advanced features such as call forwarding, IVR, call recording, and analytics, making it easy to manage large volumes of calls efficiently.

With flexible pricing plans and strong customer support, TeleCMI ensures you get a scalable and reliable communication solution tailored to your needs.

Why Choose TeleCMI?

• Seamless Integration: Works flawlessly with softphones and virtual PBX systems.
• Advanced Call Features: Offers call routing, IVR, call recording, and detailed analytics to optimize communication.
• Scalability: Whether you’re a small business or a large enterprise, TeleCMI grows with you.
• Affordable Pricing: Flexible pricing plans make it cost-effective without sacrificing quality.
• 24/7 Customer Support: Dedicated support ensures that any issues are resolved quickly, keeping your business running smoothly.

TeleCMI is the complete VoIP solution for businesses looking to streamline and improve their communication.

PBX (Private Branch Exchange), As the name suggest that a telephony system which works for a induvial organization, Extension each person will be generated. Now there a lot of technology changed, as introduction of networks over life of technology replaces alot of dependency on electronic devices. Now things are moving toward network technology alike IP (Internet Protocol). So if we define the word VOIP (Voice Over Internet Protocol) send voice over network. Its now not a tough to under now IP PBX, as network connected solution which covers internet protocol based private branch exchange, makes is whole answer. Major solution used for same are Asterisk, FreePBX, Freeswitch, FusionPBX and many more related opensource solution.

VIKAS KUMAR

Gventure Technology Pvt Ltd

In the realm of telecommunications, Voice over Internet Protocol (VoIP) and cloud PBX (Private Branch Exchange) are two technologies that are analogous to one another but also stand on their own.

Speech over Internet Protocol, sometimes known as VoIP, is a technique of transferring voice and multimedia material not over conventional telephone lines but rather over the internet. Voice and multimedia data are digitised and transferred over the internet as data packets using a technology called voice over internet protocol (VoIP), rather than as analogue signals. Phone over Internet Protocol (VoIP) technology enables a diverse range of applications, such as voice calls, video conferencing, and voice mail.

On the other hand, a cloud PBX is a kind of the Private Branch Exchange (PBX) system that is hosted in the cloud. A private branch exchange, or PBX, is a kind of telephone exchange that may be installed inside an organisation and used to direct incoming calls to the correct line. A PBX system that is hosted on a distant server, as opposed to being located in a local data centre, is referred to as a cloud PBX.

In a nutshell, voice over internet protocol (VoIP) is the process of sending voice calls and other types of multimedia material over the internet, while cloud PBX is the name given to a PBX system that is housed in the cloud. The combination of the two technologies is able to provide a full unified communications solution when it is deployed.

Yes, but you will need gateways. PSTN/TDM to SIP/VOIP GATEWAYS to be exact.

Basically gateways will convert your analog pabx to SIP/VOIP to be connected to a VOIP/SIP pabx like asterisks.

For individual analog telephone there's also ATA (analog telephone adapter) you can use to register to a SIP/VOIP PABX.

I recently made a calling service to enable calls from a mobile app to a PABX, easy deployment for SIP capable pabx but for analog pabx I normally require SIP gateways and/or Session Border Controllers (SBC), a type of SIP gateway on steroid which will also serve as a voice FW for extra security.